Fig. 5.1 Arctic-wide annual average surface air temperature anomalies relative to the 1961–90 mean, based on land stations north of 60°N from the CRUTEM 3v dataset, available online at www.cru.uea.ac.uk/cru/data/temperature/. Note this curve does not include marine observations. Fig. 5.2. Near-surface (1000 mb) air temperature in °C

anomalies for February 2009. Anomalies are relative to the 1968–96 mean, according to the NCEP–NCAR reanalysis through the NOAA /Earth Systems Research Laboratory, generated online at www.cdc.noaa.gov

Fig. 5.3. Near-surface (1000 mb) annual air temperature in °C anomalies for 2009 over the northern hemisphere relative to 1968–96 mean according to the NCEP–NCAR reanalysis through the NOAA /Earth Systems Research Laboratory, generated online at www.cdc.noaa.gov. Arctic amplification of air temperature anomalies are a factor of two or more relative to lower latitudes.

Fig. 5.4. Lower tropospheric (850 hPa) air temperature in °C anomalies for October 2009 relative to the 1968–96 mean according to the NCEP–NCAR reanalysis through the NOAA /Earth Systems Research Laboratory, generated online at www.cdc.noaa.gov.

Fig. 5.5. Simulated circulation patterns of the upper-ocean wind-driven circulation in 2007 (top), 2008 (middle) and 2009 (bottom). Annual, winter, and summer circulations are shown in the left, center, and right panels, respectively.

Fig. 5.6. Satellite-derived summer (JAS) SST anomalies (Reynolds et al. 2002) in 2007 (left), 2008 (middle), and 2009 (right) relative to the summer mean over 1982–2006. Also shown is the Sep mean ice edge (thick blue line).

Fig. 5.7. Summer heat (1 × 1010 J m-2) (left) and freshwater (m) content (right) in the 1970s, 2007, 2008, and 2009. The top two panels show heat and freshwater content in the Arctic Ocean based on 1970s climatology (Timokhov and Tanis 1997, 1998). The bottom six panels show heat and freshwater content in the Beaufort Gyre based on hydrographic surveys (black dots depict locations of hydrographic stations). For reference, this region is outlined in black in the top panel of each column. The heat content is calculated relative to water temperature freezing point in the upper 1000m ocean layer. The freshwater content is calculated relative to a reference salinity of 34.8

Fig. 5.8. 2007–09 Atlantic water layer temperature maximum anomalies relative to climatology of Timokhov and Tanis (1997, 1998).

Fig. 5.9. Mean temperature of Atlantic water (AW, defined with TAW >1°C) and the AW volume inflow in the West Spitsbergen Current, northern Fram Strait measured by the array of moorings at 78°50’N.

Fig. 5.10. Five-year running mean time series of: the annual mean sea level at nine tide gauge stations located along the Kara, Laptev, east Siberian, and Chukchi Seas’ coastlines (black line); anomalies of the annual mean Arctic Oscillation (AO) Index multiplied by 3 (red line); sea surface atmospheric pressure at the North Pole (from NCAR–NCEP reanalysis data) multiplied by -1 (dark blue line); annual sea level variability (light blue line). Dotted lines depict estimated trends for SL, AO, and SLP.

Fig. 5.11. Sea ice extent in March 2009 (left) and September 2009 (right), illustrating the respective winter maximum and summer minimum extents. The magenta line indicates the median maximum and minimum extent of the ice cover, for the period 1979–2000. (Source: National Snow and Ice Data Center.)

Fig. 5.12. Time series of the percent difference in ice extent in March (the month of ice extent maximum) and September (the month of ice extent minimum) relative to the mean values for the period 1979–2000. Based on a least squares linear regression for the period 1979–2009, the rate of decrease for the March and September ice extents is –2.5% and –8.9% per decade, respectively.

Fig. 5.13. Arctic sea ice distribution in March of 2007, 2008, and 2009. Multiyear ice is in white, mixed ice aqua, first-year ice teal, and ice with melting surface red. Dark blue is for open water and brown for land. Figure courtesy of Son Nghiem.

Fig. 5.14. (a) Winter Arctic Ocean sea ice thickness from ICESat (2004–08). The black line shows the average thickness of the ice cover while the red and blue lines show the average thickness in regions with predominantly multiyear and first-year ice, respectively. (b) Interannual changes in winter and summer ice thickness from the submarine and ICESat campaigns within the data release area for a period of more than 30 years. The data release area covers approximately 38% of the Arctic Ocean. Blue error bars show the uncertainties in the submarine and ICESat datasets (Kwok et al. 2009)

Fig. 5.15. Magnitude (unitless, left) and percentage (right) change of maximum NDVI from 1982 to 2008 for the circumpolar arctic tundra region. Colors show changes only within the area north of the Arctic tree line. Color scales are not linear (Bhatt et al. 2009, manuscript submitted to Earth Interactions).

Fig. 5.16 Above ground biomass index by plant functional type for 18 permanent vegetation plots at Alexandra Fiord, Ellesmere Island, Canada, in 1995, 2000, and 2007. Values were the mean number of living tissue hits per plot using the point intercept method. Total live vegetation, bryophytes, and evergreen shrubs increased significantly over the period at p = 0.05. (Hudson and Henry 2009).

Fig. 5.17. Changes in permafrost temperature at different depths at the Barrow, Alaska, Permafrost Observatory in 2002–09.

Fig. 5.18. Total annual river discharge to the Arctic Ocean from the six largest rivers in the Eurasian Arctic for the observational period 1936–2008 (updated from Peterson et al. 2002) (red line) and from the four large North American pan-Arctic rivers over 1970–2008 (blue line). The least squares linear trend lines are shown as dashed lines. Provisional estimates of annual discharge for the six major Eurasian Arctic rivers, based on near-real-time data from http://RIMS.unh.edu, are shown as red diamonds. Upper green line shows the September (minimum) sea ice extent in the Arctic Ocean over 1979–2009 from NSIDC (http://nsidc.org/data).

Fig. 5.19. (a) Snow cover duration (SCD) departures (with respect to 1988–2007) for the 2008/09 snow year and (b) Arctic seasonal SCD anomaly time series (with respect to 1988–2007) from the NOAA record for the first (fall) and second (spring) halves of the snow season. Solid lines denote 5-yr moving average; negative number means shorter snow season than normal. (c) Maximum seasonal snow depth anomaly for 2008/09 (with respect to 1998/99–2007/08) from the Canadian Meteorological Centre snow depth analysis. (d) Terrestrial snowmelt onset anomalies for 2009 (with respect to 2000–09) from QuikSCAT data derived using the algorithm of Wang et al. (2008).

Fig. 5.20. Anomalies in (a) summer (JJA) 2009 air temperature (°C) at 700 hPa, and (b) winter (September 2008–May 2009) precipitation (mm) in the NCEP/NCAR Reanalysis relative to a 1948–2008 climatology.

Fig. 5.21. Anomalies (relative to 2000–2004 climatology) in melt season duration and the dates of melt onset and freeze-up on Arctic glaciers and ice caps (outside of Greenland) derived from SeaWinds scatterometer on QuikScat, and anomalies in summer (JJA) 2009 air temperature (°C) at 700 hPa in the NCEP/NCAR Reanalysis relative to a 1948–2008 climatology. Melt onset and freeze-up dates define the first and last days on which melt occurred during the year. As there can be cold periods during the summer when melt ceases, the melt duration can be less than the number of days between the onset and freeze-up dates.

Fig. 5.22. Upper-air and surface seasonal and annual mean temperature anomalies in 2009, with respect to the 1971–2000 average. The station WMO ID number is indicated beside the location name. See Table 5.2 for site coordinates.

Fig. 5.23. The geopotential height and wind anomalies for JJA 2009 (referenced to the 1960–2009 mean) at 500 hPa from the NCEP/NCAR Reanalysis. Areas where geopotential height anomalies were at least twice the 1960–2009 standard deviation are hatched. The blue arrows represent wind vector anomalies, with scale indicated by the blue arrow below the plot

Fig. 5.24. Time series of Greenland regional melt extent anomalies derived from passive microwave remote sensing, after Mote (2007).

Fig. 5.25. Time series of surface mass balance component anomalies simulated by the regional climate MAR model (Fettweis et al. 2010).

Fig. 5.26. Year 2009 snowfall anomalies (mm) simulated by the regional climate MAR model (Fettweis et al. 2010). Hatched areas indicate an anomaly that is twice or more the 1971–2000 standard deviation.

Fig. 5.27. Satellite view of the Nares Strait polynya between Arctic Canada and northwest Greenland. Note the wind-driven “sea smoke” cloud streaks, that is, ice fog condensate from the much warmer ocean surface.

Fig. 5.28. Cumulative annual area changes for 34 of the widest Greenland ice sheet marine-terminating outlets.